In the process of computing optical flow, the corresponding relationship among features of sequent images isn't required. So the technique is widely used in many fields of computer vision, such as parameter estimation of moving object and target tracking. But it's rarely used in infrared image because of the high noise. Optical flow fields of some real infrared images are computed using several usual methods. The results demonstrate that the optical flow field of target which is close to real situation can be obtained while suitable methods are selected or improved. The optical flow could be used in object segmentation, moving status analysis and target tracking of infrared images.